The growing problem of antibiotic resistant bacteria (see, e.g., Chambers H. F., Emerg. Infect. Dis. 7:178-182 (2001); Hecht D. W., Clin. Infect. Ilis. 39:92-97 (2004); Jacobs M. R., Am. J. Med. 117 Suppl. 3A:3S-15S (2004); Molbak K., Clin. Infect. Dis. 41:1613-1620 (2005); Shah et al., Res. Microbiol. 155:409-421 (2004); Wisplinghoff et al., Clin. Infect. Dis. 39:309-3 17 (2004); and Zinner S. H., Expert Rev. Anti. Infect. Ther. 3:907-913 (2005)) points to a need for new anti-infective therapies. However, the rate of new antimicrobial discovery is unlikely to meet the expected need for the foreseeable future (see Boggs et al., Clin. Microbiol. Infect. 10 Suppl. 4:32-36 (2004); Bush K., Clin. Microbiol. Infect. 10 Suppl. 4:10-17 (2004); Dougherty et al., Curr. Pharm. Des. 8:1119-1135 (2002); Schmid M. B., Nat. Rev. Microbiol. 2:739-746 (2004); Silver L. L., IDrugs 8:651-655 (2005); and Walsh C., Nat. Rev. Microbiol. 1:65-70 (2003)). Specific problems include the over-mining or exhaustion of cultivable microorganisms (see Osburne et al., ASM News 66:411-417 (2000)), a high background of toxic compounds or compounds with poor pharmacokinetic properties in synthetic compound libraries (see Projan et al., Clin. Microbiol. Infect. 10 Suppl. 4:18-22 (2004); and Lipinski et al., Nature 432:855-861 (2004)), and the inability of most synthetic leads to penetrate across the multi-drug resistance (MDR) barrier of Gram-negative bacteria (see Li et al., Drugs 64:159-204 (2004)). The increased use of in vitro assays for small molecule discovery that bear little resemblance to the biological systems in which the drugs need to function may also be responsible for the decline in the rate of drug discovery (see Lipinski et al., Nature 432:855-861 (2004); Horrobin D. F., Nat. Rev. Drug Discov. 2:151-154 (2003); Williams M., Curr. Opin. Investig. Drugs 5:29-33 (2004)). Thus, there is a need for developing new antimicrobial compounds.